Extraction of oils with improved solvents



1938. A. E. BROWN ET AL 2,133,832

EXTRACTION OF OILS WITH IMPROVED SOLVENTS Filed Oct. 15, 1932 BY B M- LL.K B

ATTORNEY Patented Dec. 6, 1938 EXTRACTION 0F OILS WITH IMPROVED SOLVENTS Arthur B. Brown, Hammond, Ind., and Fred F. Diwoky, Chicago, 111., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application October 15, 1932, Serial No. 637,978

7 Claims. (Cl. 196-13) This invention relates to the extraction of oils with improved solvents and it pertains more particularly to the extraction of lubricating oils with a mixture of solvents- Petroleum is essentially a mixture of hydrocarbons comprising several groups or homologous series of compounds such asthe parafflns, hydroaromatics, aromatics, polymethylenes, and various other series in which the hydrogen to carbon ratio is even difierent from that in the above classes. A large number of individual compounds of each series are present and have different boiling points, physical and chemical properties.

In the various types of crude petroleum commonly known as paraflin base, naphthenic or asphalt base, and mixed base, these various series of hydrocarbons are present in different proportions. For example, in the paraifin base oils such as those from the Appalachian field there is a relatively high proportion of paraiiinic hydrocarbons having a chain structure and a high hydrogen to carbon ratio, whereas in the California and Gulf Coastal oils there is a high proportion of hydrocarbons with ring structures and low hydrogen to carbon ratio. The mixed base oils such as those from Oklahoma and the Mid- Continent area are in general intermediate between these two extreme types.

In the normal refining of crude petroleum, the fractions of varying distillation ranges which are successively obtained by distillation of the 011s partake of the general character of the crude; for example, lubricating oils derived from Appalachian crudes will show parafiinic characteristics, whereas the lubricating oils derived from coastal crude show naphthenic characteristics.

The distillates from the mixed base crudes, such as those from the Mid-Continent area, will show characteristics common to both the paraffinic and naphthenic oils. The crude from Winkler County, Texas, is intermediate coastal and Oklahoma crudes in its characteristics. An important property of parafllnic lubricating oils is their low viscosity-temperature coeflicient or rate of change of viscosity with temperature. This property makes them particularly suitable for certain lubrication problems where high temperatures are encountered.

At low temperatures also, these oils retain their fluidity better, an important consideration in cold weather operation of automobiles, for example.

For this reason it is very desirable to separate from the mixed base oils the undesirable naphri thenic constituents. Various methods have been proposed for doing this and some have been used with partial success. Thus, the oil may be subjected to vigorous treatment with fuming sulfuric acid, followed by neutralization and removal of harmful sulfuric acid derivatives.

The object of our invention is to provide an improved method for extracting the naphthenic constituents from mixed base lubricating oils so that the resulting oils will have improved viscosity characteristics and will contain a high proportion of paraflinic compounds.

A further object is to provide a process for treating mixed base petroleum oils without the expense of acid treatment and without the loss of valuable petroleum constituents which accompanies the use of acid treating.

A particular object of our invention is to provide a solvent which has a very high degree of selectivity for the naphthenic constituents oi. mixed base lubricating oil distillates.

A further particular object of our invention is to provide mixtures of organic solvents which have greater selectivity for treating mixed base lubricating oil than the individual solvents of the mixture.

The expression viscosity index, as used herein, refers specifically to the index defined by Dean and Davis in Chemical and Metallurgical Engineering, volume 36, 1929, page 618. The viscosity index of a lubricating oil is an indication of its composition or type, i. e., whether it is a paraffin base or naphthene base oil. Paraffin base oils are arbitrarily assigned a viscosity index of 100, naphthene base oils are assigned a viscosity index of 0, and mixed base oils lie between these extremes. By the present invention we have made it possible to obtain from mixed base lubricating oils a maximum yield of paraflin type oils (with a high viscosity index) without the nuisance or cost of acidtreating and without appreciable destruction of the naphthenic constituents of the oil. Our process comprises extracting the oil with a solvent or a mixture oi solvents wherein the components are chosen from two classes of compounds, one of these classes we call primary solvents and the other we call secondary solvents or promoters. The primary solvents comprise a group of aromatic, heterocyclic and aliphatic compounds, and the secondary solvents comprise the low boiling aromatic and the aliphatic ethers such as phenyl methyl ether, ethyl ether, isopropyl ether and mixed ethers. A more detailed description of the primary and be set forth hereinafter.

The term naphthenic hydrocarbons is employed in this application and in the claims in a generic sense to include the hydrocarbons that have a low viscosity index, a tendency to form sludge and a tendency to decrease the parafiinic characteristics of the oil. Examples of these naphthenic hydrocarbons are classified as aromatic, aromatic-like, oleflnic and polymethylene hydrocarbons.

In Figure l of the accompanying drawing which forms a part of this specification, we have diagrammatically shown an apparatus suitable for carrying out our invention. The particular apparatus described forms no part of our invention and it should be understood that other types of extraction apparatus and processes may be used for applying our special solvent mixtures.

Our invention is applicable to the treatment of any oil but particularly a mineral oil such as asphaltic and mixed base oils and in a preferred method of extracting such oils we will describe the treatment of a heavy mixed base lubricating oil distillate having a gravity of 21.6 A. P. I., a viscosity of 114 seconds Saybolt at 210 F. and a Dean and Davis viscosity index of 56.5. Generally, our process of mixed solvent extraction gives excellent results with mixed base mineral oil distillates or mixed-base residues which have viscosities within the range of 200 to 3500 seconds Saybolt at 100 F., although it should be understood that the process is applicable to any lubricating oil of lower or higher viscosities. In the preferred example we will disclose the use of the batch method wherein one volume of oil is extracted with three volumes of the mixed solvent, said mixed solvent comprising '70% of di(2 chlorethyl) ether and 30% of isopropyl ether. It should be understood that we may use a continuous process of extraction wherein the oil is contacted with the solvent countercurrently. Also the oil may be given several successive extractions with the same or different solvents.

The mixed base mineral oil distillate is introduced into the extractor III by means of the conduit II and pump I2. Any type of agitating means such as the stirrer 13, may be used for contacting the oil with the mixed solvents. A closed coil I4 is provided on the inside of the agitator whereby the contents of the extractor may be heated with steam from valved pipe l5 or cooled with water or brine from valved pipe It. The base of the extractor is preferably conical and it terminates in a discharge pipe I] which is provided with a valve 18 and glass window l9 so that the liquid flowing from the extractor may be seen.

After the step of extraction, which will be later described, the mixed solvents and naphthenic extract are withdrawn through pipe 20 and valve 2| to still 22 where the solvent is distilled from the extract. The extract is discharged from the still through pipe 23. The solvents pass up through the tower 24, around the reflux coils 25, through the pipe 26, condenser 21, and pipe 2 to the storage tank 29. The pump 30 is placed in the line between the tower 24 and the condenser 21 so that the distillation of the solvents from the extract can be performed at subatniospheric pressure, if desired. The solvent in storage tank 29 is introduced into the extractor by means of the valve 3| and pipe 32.

The oil remaining in the extractor comprises the improved oil or the fraction high in paraflins, this fraction usually being referred to as the The oil is withdrawn through pipe 33 and valve 3% and introduced into the stripping tower 35 where the small amount of solvent dissolved in it is removed by a stripping gas such as carbon dioxide, nitrogen or'the like. Steam may also be used in most cases if provision is made for drying the recovered solvent where it is being reused. If an inert gas, such as nitrogen, is to be used for the stripping, it is introduced into the stripper by means of pipe 36, heater 31, conduit heating. The parafiinic oil freed from the small portion of solvent is withdrawn through pipe 50 and valve 5|. The heating medium for the heater 31 is introduced and withdrawn through the lines 52 and 53 respectively.

In performing a batch extraction, we introduce the oil and mixed solvent into the ex-. tractor l0. Steam may then be introduced into coils M to raise the temperature of the oil and solvent high enough to obtain substantially complete miscibility, but it should be understood that different temperatures will be required with different oils and solvents. Generally, the miscibility temperature falls within the range of 50 to 200 F. During this step the oil and solvent may be thoroughly mixed by the agitator l3, in fact, if the agitation and mixing is sufliciently thorough the temperature need not be raised to effect complete miscibility. It is important, however,

to obtain thorough contact of oil and solvent.

After the oil has been thoroughly mixed, it is cooled to a temperature at which the solvent and extract separate from the paraiiinic oils or raffinate. The separation is generally made at least 40 F. below the temperature at which complete or substantially complete miscibility was obtained. The temperature at which this separation is effected is referred to throughout this application as the extraction temperature." Cooling may be effected by passing cold water or cold brine through coils M, the agitation being preferably continued during the cooling step. In this particular example, the oil and solvents were cooled to-about 10 F. and allowed to separate.

- The separation may require from one-half hour to flvehours. We prefer to use the lowest temperature at which a good separation of the paraffinic and naphthenic fractions can be obtained. This extraction temperature is usually within the range of 0 to 95 F. Also, cooling may be effected by adding propane or other low boiling hydrocarbons to the oil and then flash the same.

If the lubricating oil were not dewaxed before being extracted, the upper layer, or raflinate, may solidify or-partly solidifyon cooling. The lower layer containing the naphthenic type oil and solvent remains substantially wax-free and fluid. Usually both the oil and solvent will be in a fluid state and valve I8 is closed when the raflinate appears in the sight glass l9, then valve 2| 'is closed and valves l8 and 34 are opened to pass the paraflinic oil into the stripper column 35, as hereinabove described. We may-extract the oil a second time or as many times as desired to effect the degree of refining required.

In the abovedescribed process of operation, 35

we have used one volume of oil and three volumes of solvent, said solvent comprising 70% of di (2 chlorethyl) ether and 30% of isopropyl ether, but the ratio of the volume of solvent to 5 the volume of oil may be varied from one-half to nine volumes of solvent for each volume of oil. Also, the solvent may comprise different proportions of primaryand secondary solvents, generally from 50 to 95% of the primary solvent for each 50 to 5% of secondary solvent. When the volume of solvent is one or less to each volume of oil, we prefer to give the oil several extractions in orderto produce an oil of the desired viscosity index. 15 The following table illustrates the results obtained from the mixed solvent extraction of the Mid-Continent lubricating distillate having a viscosity of 114 seconds Saybolt at 210 F., viscosity index of 56.5 and A. P. I. gravity of 21.6. In the above process and in the following table the results are based upon the use of one volume of oil to three volumes of solvent.

By comparing the properties of the oil prepared in the above example with the properties of the oil before extraction, it will be seen that we can take a mixed base Mid-Continent lubricating oil distillate of 56.5 viscosity index and obtain an oil having a viscosity index from 86.5 to 89.5. By comparing Example 1 with Examples 2, 3 and a, it will be seen that the viscosity index of the oil prepared by the mixed solvents is higher than the viscosity index of the oil prepared by the single solvent, or primary solvent.

Instead of using one extraction or several successive extractions with the same solvent, as set 50 mixed solvent and then treated with a different mixed solvent. Also, the oil may be treated with a suitable single solvent and then this treatment may be followed with a mixed solvent extraction. It is apparent that many modifications of the hereinabove described process of extraction may be used. Also, in some cases, the extraction temperature may be as low as -40 F.

Also, when sulfuric acid is used to treat oils, the acid sludge or semi-solid material obtained thereby is a waste product. It is very difficult to burn, and the acidic nature of the material makes it very difiicult to handle. The acid fumes produced during the process of acid treatment of lubricating oils makes this process a hazardous, disagreeable and highly objectionable operation. The process of solvent extraction is not accompanied by objectionable fumes and can be very easily performed. Also the extract has not been changed chemically and it may be used as charging stock in the process of cracking for manufacturing gasoline. Also, this extract is very valuable in its original state as a fuel and as a source of naphthenic compounds.

75 It will be apparent from the above table and forth above, the oils may be treated with one I the table given below, that the selectivity of our mixture of primary and secondary solvents for the separation of mineral oils into a more parafiinic-and a less parafl'inic fraction is superior to that of the primary solvent per se.

The following table sets forth the results obtained with a halogenated ether such as di(2 chldrethyl) ether is used in combination with other organic compounds as the primary solvent, and a low molecular weight ether such as isopropyl ether is used as the secondary solvent. The oil treated in this example is a mixed base Mid-Continent lubricating distillate having a viscosity of 114 seconds Saybolt at 210 F., viscosity index of 56.5 and a gravity of 21.6 A. P. I. In the following table three volumes of solvent were used for each volume of oil.

Table II Solvent Rafiinate 1 Prlmarg all s d Exzimp e vent: i econ ary chlloreth yl) solvent 1 g i gggggg et er 85 isopropy cresyllc ar id ether Index mm Percent Percent F. 1 100 U 86. 8 40 85 15 92. 7 i 70 30 92.1 40 100 0 83. 5 8O 20 84. 8 10 6 70 30 88. 6 10 Table III Solvent Rafiinato Primary sol- Secondary Example vent: diohlorsolvent Vis- Extraction ethyl ether isopropylcosity tempera- 85%, nitroether index ture benzene Percent Percent F.

From the above tables II and III it is apparent that the combination of mixed solvents is very effective for separating mixed base mineral oils into paraffinic and naphthenic fractions of hydrocarbon oils. By comparing the results obtained in Example 1 of Tables I, II and III with the results set forth in the other examples of Tables I, II and HI, it is apparent that the selectivity of the combined primary and secondary solvents is much greater than the selectivity of the primary solvents per se.

We have used the term secondary solvent to cover the aliphatic and aromatic ethers and derivatives thereof and the term primary solvent has been used to cover the other compounds which cooperate withthe secondary solvents to give our improved results. By using this combination of solvents the resulting mixture possesses greater selectivity for the undesirable naphthenic, naphthenic-like, oleflnic and aromatic hydrocarbons present in the mixed base oil than for the paraflinic constituents of the mixed base oil.

Examples of the primary solvents which we employ are in general considerably higher bolling and higher in molecular weight than the secondary solvents and include the nitrogen substitituted aromatic compounds such as nitrobenzene, aniline, ortho meta and para nitrotoluene,

ortho-nitro anlsole, nitro xylene, xylidines, alpha and beta naphthols, such as 1-3-2-dimethyl amino benzene and 1-4-2-dimethyl amino benzene, nitro naphthalenes, ortho meta and para chloranilines, ortho meta and para chloro nitrobenzene; halogen substituted aryl compounds such as chloro benzene, ortho meta and para-dichlorobenzene, ortho chlorodiphenyl, benzylchloride, ortho meta and para chlortoluenes, ortho meta and para chlorophenols, ortho meta and para cresols, cresylic acid and alpha chloro naphthalene; other benzene compounds such as toluene, anisole and the like; halogenated ethers such as methyl Z-chlorethyl ether, methyl 2-3- dichloropropyl ether, methyl 2-chlorisopropyl ether, 2-chloroethyl ethyl ether, di(2-chlorethyl) ether, 1-2 dichlorethyl ethyl ether, l-2-3-trlchloroethyl ethyl ether, 2-bromethyl ethyl ether, 2-chlorethyl propyl ether, ethyl 2-3-dichloro propyl ether, chlorobutyl ethyl ether, ethyl chlorisopropyl ether, 2-chlorethyl chloropropyl ether. 2-3 dichloropropyl propyl ether, di(2- chloropropyl) ether, di(3-chloropropyl) ether, di(2-chlorisopropyl) ether, and di(2-bromethyl) ether; heterocyclic ring compounds such as dioxan'e, piperidine, furfural, alpha-furylacetone, thiophene, 2 3-dimethyl thiophene, 2-4-dimetl'nyl thiophene, pyrrole, methyl pyrroles,-2-alkyl quinolines, quinoline, 2-methyl quinoline, alpha-piccaldehyde, Z-chloropropionic aldehyde, chlor-acetogenated aliphatic hydrocarbons and halogenated aliphatic compounds such as ethylene dichloride, l-2 dichloropropane, 1-3 dichloropropane, l-2- dibromopropane, tetra methylene chloride, isopropyl chloride and butyl chloride. The above primary solvents are of relatively low molecular weights and most of them boil at temperatures under 260 C. Also mixture of the above compounds may be used asthe primary solvent or as the sole solvent for extracting the oil, for example, nitro benzene and aniline, nitrobenzene and cresylic acid, nitrobenzene and di(2 chlorethyl) ether, nitrobenzene and phenol, nitrobenzene and furfural, di(2 chlorethyl) ether and phenols, di(2 chlorethyl) ether and aniline, di(2 chlorethyl) ether and any of the above halogenated ethers, and other mixtures of the above primary solvents.

Examples of the secondary solvents which may be mixed in any proportion desired, but generally are the ethers, such as methyl ether, methyl ethyl ether, methyl propyl ether, methyl isopropyl ether, methyl butyl ether, methyl secondary butyl ether, methyl isobutyl ether, methyl tertiary butyl ether, ethyl ether, methyl phenyl ether, ethyl propyl ether, ethyl isopropyl ether, ethyl phenyl ether, propyl ether, propyl isopropyl ether, isopropyl ether, ethyl butyl ether,

dioxane, diphenyl ether and mixtures of the above ethers. The ethers suitable for this invention have the general formula R-O-Ri wherein R and R1 represent alkyl or phenyl radicals or derivatives thereof. The ethers used as secondary solvents are normally liquid.

The above primary and secondary solvents may be mixed in any proportion desired, but generally the mixed solvents should comprise from 50 to 95% of the primary solvent. In the majority of cases the best results are obtained when 3 to 4 volumes of solvent are used to extract 1 volume of oil and sa d solvent comprising about 70% of primary solvent and 30% of the secondary solent. Also one or more primary and/or secondline, aldehydes such as paraldehyde, parapropyl aldehyde, benzaldehyde, para-anisaldehyde, halaisassa ary solvents may be used in the admixture of solvents. The solvents used for treating the oil should be substantially free from water and the commercial grade of these solvents has proven to be very satisfactory. If the primary and secondary solvents are not reactive with Water, a small amount of water will not produce undesirable or injuriousresults.

The process of extracting the mixed base lubrieating oils with a mixture of the above primary and secondary solvents is substantially the same as set forth hereinabove with di(2 chlorethyl) ether as the primary solvent and isopropyl ether as the secondary solvent or promoter. In case the admixture of primary and secondary solvents has a high boiling point or in case the solvents have a tendency to decompose when heated to relatively high temperatures, the step of removing the solvents from the extract in still 22 should be performed at subatmospheric pressures. This step of distilling at reduced pressures may be accomplished by the use of a suitable vacuum pump.

Instead of using the extraction process as the sole means for treating the oil, it may be used to supplement a preliminary acid treat, although it is preferable to follow the'extraction process with a light acid treatment in order to improve the color and sludge stability of the lubricating oil, if desired. Usually it is desirable to finish the oil either by percolation or contacting with fullers earth at somewhat elevated temperatures. If the oil was initially dewaxed, it will usually be in a marketable condition after the step of solvent extraction, however in some cases it is desirable to clay treat the oils.

While we have described a preferred embodiment of our invention, it should be understood that it is not limited to the specific details hereinabove set forth except as defined by the following claims. Also'it is apparent that many modifications and alterations of the process can be accomplished by those skilled in this art Without departing from the spirit of our invention.

We claim:

1. The process of removing naphthenic hydrocarbons from mixed base mineral lubricating oils, which comprises extracting the oil with a solvent comprising an" aliphatic ether and a chlorinated aliphatic ether.

2. The process of treating oils containing sludge-forming constituents, which comprises ex tracting the oil with a solvent comprising an alt: phatic ether containing not more than eight carbon atoms and a chlorinated aliphatic ether containing not morethan eight carbon atoms.

3. The process of removing naphthenic hydrocarbons from mixed base mineral lubricating oils, which comprises extracting the oil with a solvent comprising a low boiling aliphatic ether and a dichlorinated aliphatic ether.

4. In the art of refining oils the process which comprises adding an admixture of isopropyl ether and di(2-chlorethyl) ether to a viscous mineral oil containing paraffinic and naphthenic hydrocarbons, heating the mixture to such a temperature as to effect solution, cooling the solution to form a two-layer system, and separating the upper layer from the lower layer.

5. In a process for producing lubricating oil having a high viscosity index from a mineral oil containing naphthenic and parafiinic constitucuts, the steps comprising extracting the oil with a mixture of solvents comprising a halogenated aliphatic ether containing not more than 75 eight carbon atoms and an ether having the following general formula: R-O-R1 wherein R and R1 represent alkyl or phenyl groups.

6. In a process for producing lubricating oil having a high viscosity index from a mineral oil containing naphthenic and paraflinic constituents, the steps comprising extracting the mineral oil with a mixture of solvents comprising a chlorinated aliphatic ether containing not more than eight carbon atoms and an ether of the following general formula: R-O-R1 wherein R and R1 represent alkyl or phenyl groups.

CERTIFICATE Patent No. 2,158,852.

ARTHUR B It is hereby certified that error of the above numbered patent requiri column, line 52, I but generally" solvents; and that the said Letters rection therein that the same may conform to the Patent Office Signed and sealed this 10th day of January, A. 'D.

(Seal) 7. In a process for producing lubricating oil having a high viscosity index from a mineral oil containing naphthenic and paraflinic constituents, the steps comprising extracting the mineral oil with a mixed solvent which contains an aliphatic ether containing not more than eight carbon atoms and a beta-chlorinated aliphatic ether containing not more than eight carbon atoms, to form two liquid layers, separating said layers and removing the solvents therefrom.

ARTHUR B. BROWN. FRED F. DIWOKY.

OF CORRECTION.

December 6, 1958., BROWN, ET AL.

appears in the printed specification ng correction as follows: Page 1 first strike out the words "mixed in any' proportion desired, and insert instead used in combination with the primary Patent should be read with this correcord of the case in the Henry Van Arsdale 'Acting Commissioner of Patents. 

